To prevent the inorganic salts from the phosphoric acid within the WP electrochem solution mixes adhering to the surface and causing deposits. As these deposits give a white milky "ghosting" effect, that is not cosmetically appealing. Just washing with water after does not stop this from occurring
To reduce your excess / waste fluids pH levels & to help assist with complying to your local water authority regulations
Slowly tip the spent fluid / wash off of the WP standard electrochem solution from your job into a large ( eg: 20 ltr ) plastic container containing 10 ltrs of cold water - to form approximately a 1:10 dilution of WP standard electrochem solution to water (being careful not to spill/splash). Then slowly add some WP Acid Neutralizer, you will notice a strong bubbling / fizzing carbon dioxide reaction. Let this settle then stir slowly adding some more Neutralizer keep repeating this until the reaction subsides and the fluid goes a light pink colour this is the pH indicator in the WP acid neutralizer advising that the acid is now neutralized.
You will need approximately a 3:1 ratio of WP Acid Neutralizer to WP Standard electrochem fluid
You will need approximately a 5:1 ratio of WP Acid Neutralizer to WP Power Plus electrochem fluid.
Note: Your system comes with a spare Neutralizing sticker to place on your chosen plastic 20 ltr container / tub
Once completed you should test your solution with either a pH meter or strips to obtain a pH reading. Once the waste is neutralized to a pH of > 7.5 it is generally okay to dispose of down the sewer system, though you should always consult & comply with your local regulating agencies and review your operation in terms of the applicable federal/nation or local regulations before disposing.